Explicit Precedence Constraints in Safety-Critical Java

Safety-critical Java (SCJ) aims at making the amenities of Java available for the development of safety-critical applications. The multi-rate synchronous language Prelude facilitates the specification of the communication and timing requirements of complex real-time systems. This paper combines Prelude and SCJ in order to benefit from the advantages of both approaches. An obstacle we encountered when combining these approaches was that Prelude relies on a scheduler that observes precedence constraints, but SCJ does not provide adequate support for this. Therefore, we propose an extension of SCJ to provide explicit support for precedence constraints. We present the considerations behind the design of this extension and discuss our experiences with a first prototype implementation based on the SCJ implementation of the Java Optimized Processor.